Fast Identification and Characterisation of Non-Linearities in Experimental Modal Analysis of Large Aircraft

Abstract

The vibration characteristics of aerospace structures are investigated in so-called ground vibration tests on aircraft or dynamic qualification and modal survey tests on space structures like satellites. The experimental determination of the vibration characteristics is referred to as experimental modal analysis, which is based on linear procedures. Non-linearities are not investigated in detail in these tests. Nowadays, the consideration of non-linearities in the aeroelastic stability certification processes is becoming more and more important. If non-linearities are considered in the test strategy, the experimental acquisition of the non-linear vibration characteristics can be accelerated. The aeroelastic behaviour of high flexible aerospace structures cannot be sufficiently described on the basis of linear models. Well established procedures and a new method for the detection of non-linearities are investigated and discussed in this paper with regard to their application during industrial large-scale testing. Some of the techniques are proposed for implementation in existing test strategies. A simple modal model is presented for the identification and characterisation of non-linearities, that can be efficiently handled and used to reduce testing time while simultanesously improve the quality of the test data. The modal identification procedure is utilised afterwards for the effective enhancement of present identification and qualification strategies.